Carburetor



I July 20, 1948.

M. E. CHANDLER CARBUREI'OR Filed Aug. 15, 1943 mzazm 2. #52:

2 Sheets-Sheet 1 I INVENTOR- V MLTmEZL'anmnd y M. E. CHANDLER 2,445,389

CARBURETOR Filed Aug. 15, 1943 2 Shee'ts-S heet 2 INVENTR SE ES me HowMLTU/V E EHHNQLER AGENT Patented July 20, 1948 by mesnenassignments, toNiles-Bement-Pond Company, West Hartford, Conn, a corporation 'Newq r erAmman August 13, 1943, Serial No. 498,471

The present invention relates to carburetors for internalcombustion-enginesior use on aircraft, and particularly to means forcontrolling the fuel to-air ratioin-such carburetors: Internalcombustion engines-such as those used in aircraft, operate mostefficiently ona lean mix.- tureiotiuel .andair. WI t istdesirablehowever, in order to secure the maximum power output of the engine tooperateon a: somewhat richer mixture. v.Also, the engine runscooler on,a richer mixture and henceflit. isvidesirable, when operating with.adverse cooling conditions ,such as are encountered at highaltitudes-or during a climb, to operate the engineonaa rich mixture.

Aircraft engines ;of conventional construction are usually provided withmanual minturetcon trols whereby thepilot may shift from aleanto a richmixture or vioe-ve-rsa. It sometimes occurs claims (01. 123-119) thatthepilot iorgets to change themixturecon-l trol to correspond with thechanging flight com ditions he encounters. .This mayresult in excessive.fuel consumption, if the mixture control is left in a rich position,orit mayeresult in dan gerous overheating of the engine iitthe mixturecontrol is left in its lean positions It is; therefore-tan object ofithepresent invention to provide .meansresponsive, to-.the flight conditionsencountered byvv anaircraft ,for', controlling the fuel to air, ratio.-.Another object of theapresent invention is tolprovidemeans respon:sivepto-the, rate of change .oialtitudeof an aircraft for controlling?the :fuel to .air ratio.- Another object is to'Iprov-ide meansresponsive to the quantity of airentering thacarburetor to enrich themixture of fuel and airwhenthequantity of air exceedsa'predeterminedamount i A further object is toLprov-ide mixturelcontrolmeans which is=or erable,inv atplu-rality of stages. A further.wobjectis to provide a multiple stage mixture control which. operates toincreasethe fuel to air ratio in responseto a {flight condition of theaircraft, and which operates to additionally increase thefuel toairratioinresponseto the quantity .oftairentering the, engine; V Otherobjects. andnadvantages oftthe presen invention will'become apparent.from a consideration of the appended specification,=.c1aims,;-anddrawing inwhich t Figure '1 is a somewhat diagrammatic illustration of acarburetor adapted for use with an aircraft engine and provided with amixture control arrangement embodying my invention, r 4 Figure 2 is agraphical illustration of the relationship between the fuel and airratio and ai flow in the carburetor of Figure 1, and p Figure 3illustrates an alternative form of control device which may be used inthe carburetor of Figure 1. ,c

In Figure 1, there is shown a carburetor body portion Ill. thru whichair flows from an inletgi I, thrua passage 12 to an outlet l3. Inflowing thru thepassage 12 the air passes thru a Venturi restriction I4,pasta throttle I5, and a fuel .discharge nozzle I6. 4

-A-second air passage connects the inlet H and the throat of venturi M.This second air passage may be traced from the inlet II thru a pluralityo-fimpact tubes 11, Whose open ends project into the inlet H, a ventring passage 18 interconnect; ing the impact tubes 11, a conduit 2|],anexpansible chamber 24 in a fuel regulator unit 25, arestriction 26,another'expansible chamber 2] in the-fuel regulator 25, a conduit 28, achamber 33 and a conduit 34 to the throat of venturi i4; 1 I A A bellows35 is mounted in the chamber 33, and operates-a valve 36 which controlsthe flow of air from therconduit 32 into the chamber 33. The bellows 35is preferably filled with nitrogen or other temperature responsivefluid, so that the position of valve 36 is determined by the temperatureandpressure of the air in the chamber 33,, and hence by the density ofthat air. I v V a -The,valve 36-restricts the flow of air to the secondpassage just described in such a manner that the pressure differentialbetween chambers 24 and 21 is an accurate measure of the mass of airgoing thru the passage l2. Errors due to changes in the density, of theair with altitude and temperature, and also those errors due totheinherent limitations of .a metering restriction of the Venturi type, aresubstantially eliminated by the operation of valve 36. This type oialtitude and metering error compensation is more com!-pletely-desc-ribed and claimed in my co-pending application ,Serial No.490,281, filed June LU, 194 3, now Patent Number 2,383,144.

The fuel passing thru the carburetor comes froma'fuel pump .or othersource of fuel under pressure (not shown) Frorn that source the iuelpasses thru a conduit 31, the fuel regulator unit 25, a conduit 33, ajet system 40, an idle valve 49, a conduit 4!, a pressure regulator 42,and a conduit 43 to the discharge nozzle 15.

The fuel regulator unit 25 comprises a housing 44, which is divided bythree flexible diaphragms 45, 46, and 41 into four expansible chambers48, 24, 2'! and 55. The diaphragms 45, 46 and 41 are all attached to avalve stem 5!, by any suitable means. The valve stem 5| carries abalanced valve 52 at its lower end. A compression spring 53 acting onthe diaphragm 45 biases the stem 5! for movement of the valve 52 towardopen position. a

The pressure in chamber 50 is the same as that existing on the upstreamside of the jet system 40. Chamber 4-8 is connected thru a conduit 54 tothe conduit 4! on the downstream side of the jet system 45. Thediiferential between these pressures is a measure of the quantity offuel flowing thru the jet system. This pressure differential istransmitted to the chambers 48 and 50, as described above, where it actsthru the diaphragms 45 and 47 in a direction tending to close.

the valve 52. As previously pointed out, the pressure differentialbetween chambers 24 and 21 is a measure of the mass of air flowing thruthe passage l2. This air pressure difierential acts on the valve 52 inan opening direction. It may be seen that the valve 52 is positioned inresponse to changes in the air pressure differential to produce abalancing change in the fuel pressure differential. Therefore, the valve55 controls the quantity of fuel flowing thru the carburetor inaccordance with the mass of air flowing thru the passage l2.

- The idle valve 49 is provided to control the flow of fuel when the airflow is small, as when idling the engine. The idle'valve 49 is connectedto the throttle l5 for concurrent operation therewith, by means of alinkage generally indicated at 59. At low air flows, it has been foundthat the pressure differential between chambers 24 and 21 tends to beerratic. The spring 53 and idle valve 49 have been provided to controlthe fuel flow at such times. At low values of air flow, the force ofspring 53, urging the valve 52 toward open position, overrides the forcedue to the pressure differential between chambers 24 and 21, therebymoving valve 52 in an opening direction. The connection between thethrottle l5 and valve 49 is so designed that the valve 49 isretracted toa position where it does not appreciably restrict the fuel flow when thethrottle is out of a range of positions near the closed position,sometimes termed the idling range. As the throttle moves into the idlingrange, the valve 49 is moved to restrict the fuel flow, and thisrestriction of the fuel flow becomes greater as the throttle movestoward closed position. In effect, the control of the fuel flow istransferred from the air flow responsive regulator 25 to thethrottle-controlled idle valve 42 when the latter is in its closed ornearly closed positions.

Fuel entering the jet system 40 from the condlllt 38 passes into achamber 55. The fuel may across the jet system 40 becomes large enoughto overcome the spring. Therefore, the valve 58 operates toautomatically enrich the fuel and air mixture supplied to the enginewhen the load on the engine is high.

The valve 6| has a main body portion of cylindrical form whose endcooperates with an annular seat 64 surrounding the entrance torestriction 60. The valve 6| is also provided with an elongatedprojection 65 of somewhat smaller cross-section than the restriction60'. This projection extends completely thru the jet or restriction ,6!)when the valve 6| is'plojsed against the seat 5 shown in the drawing.

A spring 56 biases the valve 6| to closed position. The valve 5| may beopened against the force of spring 66 by a pair of electro-magneticcoils GT and 68. When the coil 51 is energized, the valve 7 6| ismovedto a partly open position, wherein the main body portion of valve 6| isseparated from the seat 64, but the projection 65 extends into andpartially obstructs the restriction 60. When the coil 68 is alsoenergized, the valve BI is moved farther to the left from the positionshown, to a point where the projection 65 is completely withdrawn fromthe jet 60, which is then fully opened. In the system shown in Figure 1,the energization of coil 61 is controlled either by an altituderesponsive switch unit 3! or by an attitude responsive switch 10. Theenergizationof coil 68 is controlled by an air flow'responsive switch22'. The switch units 22 and 3| are both located in a casing II, inwhich they are separated by a, wall 59, apertured at 9|. I

The switch 3! is in the lower portion'of casing H, which is divided by aflexible diaphragm 72 into a pair' of expansible chambers 30 and 13. Thediaphragm 72 carries at its center a bridging contact 14, whichcooperates with a pair of stationary contacts 15 and 16. A compressionsprin 11 biases the diaphragm 12 in a direction to separate contact 14from the stationary contacts 15 and 76. The chamber 30 is connectedthrough aconduit 32 tothe chamber 21 of fuel regulator 25. The chamber13 is connected thru aconduit 18 to the chamber 33. Therefore thepressure difference flow out of the chamber 55 either thru a fixedrestriction 56, a restriction 5'! controlled by a poppet valve 58, or arestriction 6U oontrolledby a valve 61. Fuel flowing thru therestrictions 5'! and 60 must also pass thru another fixed restriction 62before passing out of the jet system 4!] into the conduit 4 I.

The poppet valve 58 is biased to closed position by a spring 63, and isopened against the action of this spring only when the pressuredifferential between the chambers 30 and I3 is determine-d by thepressure differential across valve 3 3. This pressure differentialvaries with the altitude of the aircraft, since the va1ve36 is operated.by bellows 35 inaccordance with the density 'of'the air. As thealtitude increases, the bellows 35 expands moving the valve 36 towardclosed positi on,.and thereby'ino'reasing the pressure differentialbetween chambers 30 and 13. The diaphragm 12 then moves downwardlyagainst spring 11. When the aircraft rises above a predeterminedaltitude, the bridging contactv 14 engages contacts 15 and IB. Thepressure differential between chambers 30 and 13 also varies with thequantity of air flowing thru the passage l2. Therefore, thealtitude atwhich the contacts of switch unit 3| are closed varies with the airflow. The altitude and air flow characteristics of the switch may bedetermined by the characteristics of spring 11. For example, the spring11 may be chosen so that at sea level, even with maximum air flow, theswitch contacts are not closed. 0n the other hand, the spring 11 may bechosen so that at sea level, the switch closes when a predetermined airflow, which may be that indicated by the ordinate passing thru the pointI05 in Figure 2 is exceeded. Then at any other altitude, abov'e'sea1evel., the switch closes at a lower value of air flow.

The attitude responsive switch 10 is illustrated ncnduluur. tie-warmers.a qtabiec ntact .41 which cooperates with a stationary contact 831,henen ulumfliis a ei o h t iisn th aimrait-t l sunwardim s c imbms heontest .1. smqved to en a e. o ta t l Whenan aircraft is .in itsnormalwflyingposrics, thefittin ;forceum ucrdmrthemizement ai -th a t ret. the. nes. is: a maxmiu and e. frictio al resistanc of. e.- w ng. to.crement thru1 the. air. i a minimum, In other words, he. Iift-t u drag:ratio. of; the, aircraft is a maximum. the aircraft departs from. this.norm l fl in position, the, lifting force is decreased. and; the; aisiucreased. With a giyenhorscpowerout, out from the engine, the. Speed.ofitheaircr it will: be. a mammum when the lift tcrdragz ratio. is a.maximl'llm As; the lift-to-drag ratio. changes, due, to. climbing, of;the aircraft or from. other causes such as improperload distribution,the speed of. the aircraft for: a. giyerr power out-put is decreased; Astheair speed: decreases, the, flowofi cooling air; over-- t e enginedecreases.) Likewise, in. an. air.- craft having a liquid cooled engine.the flow of cooling air thru the radiatordecreases It may: thcreiore.be: stated that the attitude; oi the. aircrait, as; measured by thependulum 8D: is an in.- icatiorr of the variation in the cooling. oithe. engine. I

pendulum as is also. affected by. acceleration and deceleration of. theairc-ratt. The;- action oithe pendulum. in response to acceleration isto increase the tuei-to-air ratio upon; acceleration,- ami todecreasethe f-uei-to-air ratio upon cteceleration. It therefore tends toincrease the fueleto-air ratio as. the. power output at the engine Iincreases and tov decrease the tuei-to-air: ratio as. the poweroutputdecreases. The; efiiect of; the response oi the: pendulum; 8.11 to.acceleration is. therefore beneficial, althoughit is incidental, t the:primary object oi the present invention.

The. altitude switch. if; is an: dication orthe iiectiveness 01..- theair flowin p st t e. ngine or radiator as a cooling agent. The thermal.conu ty o the ai vari s w th its densitm Asthe" d n y; decreases at higha titudes it becomes less: eifisi nt a med um,- for transfierri-n lreato the enginethe e gine. here ore ends to hotter.

Whe eith he: alt tude or'th attitude or th a rc aft ssumes a value whichindicates the P es nc of advers oo n c ndi ousrone at t e: ii h t o itis clcse s sie c ilisci s c-- tail h r i a te c osur o eit er o ih ssswt lies cause enrichmen I th m ture o inch and ai 's ipe ied o he. enemwhich qesrsthc en.- gine operating temperature.

r the a r f w sw h un t 32 i i thwPr -mries ea n h s'ssraia d by a d lhas #4 n o p si e ch mbers 4! nd The. diaphragm- 134 carries at ts centerahridg -g n a 86 which c s rei s with of $.97 ime o at s tl te 88- Mm essta ce 0 mew time 5 qu l ties tessvar ate he Ctit 8 5- om t e sta ionarycontacts 81 and 88".v "The chamhei 2!, is cor -necteg. t n- 111i. nd tZ; i am .4 in he Ri l r u ato it Chamber 8.5 i cpnrlected thr'u'theaperture- 9.! to chamber 3!). ans thehc'e thruconduit 32 to her. 2! in11611 regulator The. pro sure ential between chambers 2! and. is the thesame as. that existing. between haifihrs Z5 and Z1. {is preyiouslfif'desc'rihed',v this r n al a l es 'e Qfihs s J br h pas e s I- Wheri'the.fliq rsthm P ssa 4;? x e s j. I1.

valu contact. is. moved dow wardly and.

bridges. the. contacts fiandzll f he.pressurere ulatorfn.is;providedtoma n.- tain. the. ressureom the. downstream. sidcjotthe jet system 40at a value greaterjhainj'atmospheric. The pressure regulator 42 includesa ber' at a value greater than the atrriospheric pressur in chariibef Inthis way,"it is as: stired that thefuel' issues from nozzle [6 at a;pressure greater than that inthe passage [2, therebimininiizing anytendency of the'i'uel to vaporize iuthecoiiduit flor nozzle l3;

Operation of Figure 1- Witch tlot ircraft is 0 r it n. 6359 fli ht 4 wh. unit 39% not. lo e. its more t e. re?

muonsmp between the fuel and air r atio andthe air flow is. illustratedby the curve Figure 2- As a rflow incr ase om e o fu l? flows. ol lr hruthe. Je until the. oi ".10 'o'itcutvs i re ei e u e a r s he "1s 5. brp. suflicierit to open valve '58 against the tens u f. sp i .3.- The.uel and; air atio. then be omic r fs ing r ich. e lt s i ow. n r sesthis enricheoir g' oi the miigture being limited y the. fixectrestriction 52; The foregoin 0p n takes place. 01 1.55 WhQE the spri i16 is 'chQSQfi so that sw t h all does not. clos its. contacts, even atmaximum air. flow, at the particular attitude cohsi denedlf When. theair craft. is operating under altitude and air flow conditions such thatswitch 3i is: closed,- or it iscliinbi ng, the relation of fuel] and airratio to the air flow is illustrated by the curve Bin rg 'gure 1. Forexa ple; a su thatthe aircraft is. operating at an altitude and air flowsuch that'th'e switch 3|"moves cont-act M into: engagement with contacts15 arid, 16, Au. energizing circuit for coil 6-! is then complted; whichmaybe traced from the upper terminalfof a. battery I01 thru. a conductorI02, contacts 15; 14" and l6, a conductor I03, a corid'uctor IM, coil:61-, a conductor I05, to the lower terminal oi battery tilt.Energization of coil- 61 causes. yaliieffilto. move off. its seatIaugithe jet Bll' ilstheii partialli 'opened, beir grestricted; ily he iqiflow increases beyond the value. 'epoii it IE3 or! curVeB, theswitchtsc 8 in o e em t i h co es and m l tes an: na tin TY iti s i 5%.which ma be tra edrom the upper terminal of battery I!!! thru conducori12 c nt c s 1.4 an duc orsm3 and. Iii-I, contacts 81, 86 and 88, aconductor 't i d iq l fih 'lq sr rm-ina-l ofbattery lflL' Epergizatiouqt coil figtcauses projection 65 tolhe compietel-y moved out of jet. 6thereby enriching the fuel andairflrriixture; as-

in sated 'byth e. curVe'B. between: the points More that ther i let 9.1scutt eswitch on the operation of the system is the same as that ofaltitude switch 3| since the two Operation of Figure 3 There is shown inFigure 3 a switch mechanism which is operated in accordance with therate of change of altitude of an aircraft. This switch mechanism may besubstituted for the attitudeswitch E8 of Figure 1. Referring to Figure3, there is shown a generally cylindrical casing 2B0 attached to a base2m by any'suitable means such as the bolts 202. Inside the casing thereis mounted on the base 2M a flexible bellows 203. A spring 204 iscompressed between the bellows 253 and the base L .A pair of guidemembers 235 and 265 project from the base 20! and maintain the spring204 in proper alignment. The exterior of bellows 203 is exposed toatmospheric pressure thru a suitable aperture I99 in the casing 200. Apassage 20! extends horizontally from the space adjacent the exterior ofbellows 283 to a vertical passage 20!! which extends upwardly thru thebase 2M and is concentric with the bellows 203 and an elongated nozzle 2I connecting the passage 293 with the interior of bellows 203. nozzle2H] is of a very narrow cross-section, and restricts the flow of airbetween the exterior and interior of bellows 263.

As long as the aircraft is operating at a constant altitude thepressures inside and outside the bellows 233 are equal. When theaircraft changes its altitude, for example by climbing,

the pressure outside the bellows decreases due to the increase inaltitude. This change in pressure is not immediately communicated to theinterior of bellows 263 because of the restriction in nozzle 2 ll"...Since the pressure inside the bellows 203 is then greater than'thepressure outside, the bellows tends to expand. The force acting toexpand the bellows is proportional to the rate of change of altitude ofthe aircraft.

A rod 2H is mounted on the free upper end of the bellows 203. The rod 2Hextends thru a bushing 2| 2 in a portion of a casing 298, and near itsupper end carries a movable switch contact 2 l3 which cooperateswith astationary contact 2H,, The structure is such that when the aircraft isflying level the contact 2l3 is below and spaced from the contact 2M, asshown in the drawing. When the aircraft starts to rise, the contact 253is moved upwardly by an'amount depending upon the rate of climb. When,the rate of climb exceeds a value determined by the characteristics ofthe bellows 203 and spring 204, contact 2J3 is moved into engagementwith.

contact 2M. This completes a circuit between terminals H5 and H6, whichcorrespond to the terminals having the same reference numerals in Figure1.

Stationary contact 2M is in the form of a, disc mounted between twoinsulating plates 2l5, which are held on'the top of the casing 209 bybolts 2H6. The circuit between terminals I I5 and H5 may be traced fromterminal II 5 thru a conductor 211, a connector 2H3, a conductor 220,binding post 22L casing 2B0, rod 2, contacts H3 and 2%, a conductor 222,connector H8 and a conductor 223 to terminal I [6.

The operation of the system when the switch unit shown in Figure 3 isused therein is similar tothe operation when the switch unit 10 is used,

The passage thru and it is believed no further description of thisoperation is necessary.

It should be noted that the switch mechanism of Fig. 3 and the switches3| and 10 of Fig. 1 are responsive to conditions-which-affect thethermal capacity of the air passing the engine and therefore affect therate at which heat can be dissipated from the engine. This is true ofboth air cooled and water cooled engines. Water cooled engines dependfor their ultimate cooling on the ability of a radiator to dissipateheat to the outside atmosphere. As the density of the air decreases, itsspecific heat decreases and, therefore, the'thermal capacity of a givenvol ume of it decreases. It is, therefore, not possible to dissipate asmuch heat from the engine. Similarly, when the aircraft is climbing, itsforward speed is slower and the quantity of air passing the engine isdecreased so that the thermal capacity of the air is decreased and itcannot be cooled as efficiently. Under such conditions, it is desirableto enrich the mixture of fuel-to-air supplied to the engine so that itstemperature will not rise as high.

While I have shown and described certain preferred embodiments of myinvention, other modifications thereof will readily occur to thoseskilled in the art, and I therefore intend that my invention shall belimited only by the appended claims.

' I claim as my invention:

1. In a fuel supply system for an internal combustion engine, aconduitfor air flowing to said engine for combustion purposes, meansassociated with said conduit fOlfpl'OdllCiIlE' two unequal pressureswhose difference is a measure of the rate of flow of air thru saidconduit; a conduit of said restriction when said differential exceeds apredetermined value to increase said fuel-to-air ratio, and additionalmeans responsive to a condition affecting the thermal capacity of theair passing said engine for increasing the cross-sectional area of saidrestriction to increase said fuel-to-air ratio when said conditionassumes a predetermined value indicative of insufiicient cooling of saidengine.

2. In a fuel supply system for an internal com bustion engine, a conduitfor air flowing to said engine for combustion purposes, means associatedwith said conduit for producing two unequal pressures whose differenceis a measure of j the rate of flow of air thru said conduit, a conduitfor fuel flowing to said engine, a metering restriction in said fuelconduit for regulating the'flow thru said fuel conduit as a function of,the fuel pressure differential across said restriction, means forcontrolling said fuel pressure differential as a function of thedifierence of said two unequal pressures so as to maintain asubstantially constant'fuel-to-air ratio as long as the cross-sectionalarea of said metering restriction remains fixed, and means responsive toa condition afiecting the thermal capacity .of the air passing saidengine for suddenly and substantially increasing the cross-sectionalarea of said restriction to when said dd di-- increase-s id fuel-to-airas V I 7 are indicative or thin assumes apr'eueterm ed instrumentcoolingof'sai die I'nafiiel supplysvst'e'infor' 'iijintein'alcambustionenginefa'cond t' for flowing to'sa'id engine for combustion"pu poses, "a conduit for fuelflowing tosai'de'ngine nsior ceiitr'oumgthe relationship of 'sa'id'air "l tain asdb'stantially constantfuel-to-air atio, andmeans responsive to "a condition affecting thethermal capacity-"of the air passing said engine for suddenly andsubstantially increasing said fuel5toair ratio when fsaidc'onditionassumes a predetermined value indicative of insuific'i-ent coolingofsaid'engine. I

In a fuel suppiy system fo""a"n' intefriai'c'd'mbustion engine, aconduit for air flowing to said engine for combustion purposes, aconduit for fuel flowing to said engine, means for controlling therelationship of said air and fuel flows to maintain a substantiallyconstant fuel-to-air ratio, means responsive to the load on said engineand effective when said load exceeds a predetermined value to increasesaidfuel-to-air ratio, and additional means responsive to a conditionaffecting the thermal capacity of the air passin said engine forsuddenly and substantially in creasing said fuel-to-air ratio when saidcondition assumes a value indicative of insufficient cooling of saidengine.

5. In a fuel supply system for an aircraft internal combustion engine, aconduit for air flow-- ing to said engine for combustion purposes, meansassociated with said conduit for producing two unequal pressures whosedifference is a measure of the rate of flow of air thru said conduit, aconduit for fuel flowing to said engine, a metering restriction in saidfuel conduit for regulating the flow thru said fuel conduit as afunction of the fuel pressure differential across said restriction,means for controlling said fuel pressure differential as a function ofthe difference of said two unequal pressures so as to maintain asubstantially constant fuel-to-air ratio as long as the cross-sectionalarea of said metering restriction remains fixed, means responsive tosaid fuel pressure differential for increasing the cross-sectional areaof said restriction whensaid differential exceeds a predetermined valueto increase said fuel-to-air ratio, and additional means responsive tothe rate of climb of said aircraft for suddenly and substantiallyincreasing th crosssectional area of said restriction to increase saidfuel-to-air ratio when said rate of climb assumes a value indicative ofinsuflicient cooling of said engine.

6. In a fuel supply system for an aircraft internal combustion engine, aconduit for air flowing to said engine for combustion purposes, aconduit for fuel flowing to said engine, means for controlling therelationship of said air and fuel flows to maintain a substantiallyconstant fuelto-air ratio, and means responsive to the rate of climb ofsaid aircraft for suddenly and substantially increasing said fuel-to-airratio when said rate of climb assumes a value indicative of insufficientcooling of said engine.

7. In a fuel supply system for an aircraft internal combustion engine, aconduit for air flowing to said engine for combustion purposes, aconduit for fuel flowing to said engine, means for controlling therelationship of said air and fuel flows to maintain a substantiallyconstant fuel-to-air ratio, means responsive to the load on said engineand effective when said load exceeds 10 a predeti'minedvalii to increasesaid fuel -to-air 'r'a i0, and addition ma: es'p'on'sive'to the rate ofclimb of said-airs" aft for increasing said fuelto airratiowh'msaid'rate of climb assumesa value indicative "of insufficientcooling of said engine.

'BQI'n a fuel sites svstem'for an internal coir ensues engines conduitfor air "flowing to said engine for combustion purposes, meansassociated with sweetnessiorsrtauein two unequal pressures whosedifference is a measure of the rate of new of air thru said conduit, aconduit for fuel nowhere-said engine, a metering restriction in saidfuel conduit for regulating the flow'thi'u said fuel conduit as afunction of the fuel pressure differential across said restriction,means for controlli said fuel pressfiredifferefitiaf'as a funtioii'fifthe difference said two' 'iiiiqiim pressures so as to maintain asubstantially constant fuel-to-air ratio as long as the cross-sectionalarea of said metering restriction remains fixed, valve means forcontrolling the cross-sectional area of said restriction, electricalmeans for operating said valve means including a pair of electricalcircuit-s, first motor means connected in one of said circuits andeffective when said circuit is completed to move said valve means to apartly open position, second motor means connected in the other of saidcircuits and effective when said other circuit is completed to move saidvalve means to a fully open position, first switch means connected inboth said circuits, means responsive to a condition affecting thethermal capacity of the air passing said engine for closing said firstswitch means and thereby completing said one circuit, second switchmeans connected in said other circuit in series with said first switchmeans, and means responsive to the rate of flow of combustion air tosaid engine for closing said second switch means and thereby completingsaid other circuit when said first switch means is also closed.

9. In a fuel supply system for an internal combustion engine for use onaircraft, in combination, a plurality of parallel conduits for conveyingfuel to said engine, valve means for controlling the flow of fuel thruone of said conduits, means biasing said valve means to closed position,electrical means for operating said valve means selectively to anintermediate position or to its full open position against the action ofsaid biasing means, first switch means for controlling the energizationof said electrical means, said first switch means being effective whenclosed to cause energization of said electrical means so as to operatesaid valve means to said intermediate position, means responsive to acondition affecting the thermal capacity of the air passing said enginefor operating said first switch means to closed position when saidcondition assumes a value indicative of insufficient cooling of saidengine, second switch means for controlling the energization of saidelectrical means, said second switch means being effective when closedto cause energization of said electrical means so as to operate saidvalve means to said full open position, and means responsive to thequantity of air for combustion purposes flowing to said engine foroperating said second switch means.

10. In a fuel supply system for an internal combustion engine for use onaircraft, in combination, means for controlling the flow of fuel to saidengine in proportion to the quantity of air flowing'to said engine,first means for increasing the ratio of fuel to air, second means foraddi- 11 tionally increasing the ratio of fuel to air, means responsiveto a condition afiecting the thermal capacity of the air passing saidengine for operating said first means when said condition assumes avalue indicative of insufficient cooling of said engine, and meansresponsive to the quantity of air flowing to said engine for operatingsaid second means when said quantity exceeds a predetermined value.

MILTON E. CHANDLER.

REFERENCES CITED UNITED STATES PATENTS Name Date Bourne Nov. 26, 1912Number Number 12 I Iame --.Date Hicok et al., Aug, 25, 1925 Mabee et a1;May 17,1932 .King et'al. Aug. 2, 1932 Barker et a1. .......L.. May29,1934 Loeifler Aug. 10, 1937 Mennesson Feb. 18, 1941 Campbell Apr, 28,1942 Thompson Dec. 22, 1942 Weiche Sept. 28, 1943 FOREIGN PATENTSCountry Date I Great Britain July 25, 1940 Great Britain Jan. 27, 1942France Sept. 26, 1939

